This invention relates generally to systems for marking macro-organisms, and more particularly to a method for marking macro-organisms such as fish through the use of metallic tags having identifying characters thereon.
For many years, biologists have been attempting to track the migration patterns of animals. Particular emphasis has been placed upon studying the migratory habits of fish. There are several reasons for this, but perhaps the most important reason is because of the susceptibility of fish to environmental damage and to over-fishing. In recent years, the increasing use of hatcheries for propagating, growing and subsequently releasing migratory fish, such as salmon, has led to a strong emphasis upon developing an appropriate method for marking such fish. Because the fish are at the fingerling size when released from hatcheries, there has been a real problem with developing a system for indelibly marking such fish without harming them.
A system has been developed whereby a minute piece of wire, commonly called a tag, is inserted into the cartilaginous region of the nose of the fish. The wire tag is typically magnetized so that when the fish return to spawn, biologists can sort out those fish which have been tagged. The tags are indelibly marked so that the time and place of release can be determined.
One method for indelibly marking a wire tag is disclosed in U.S. Pat. No. 3,545,405 to Jefferts. This patent teaches a system of marking the wire with a plurality of spots in a predetermined pattern. That pattern is typically in binary form, which will enable the biologists to identify the tag and thereby determine the movements of the host fish.
The spots are applied to Jefferts' tag by directing an electrical discharge onto the surface of the wire, thereby burning a pin-point portion of the wire. A pattern of such spots is applied circumferentially around the wire and along its length. Upon subsequent retrieval of the tag, a trained biologist can read the code and determine the migratory pattern of the host fish.
While Jefferts' system provides a means for indelibly marking the tag, the marking operation is cumbersome and requires complex, expensive equipment which must either act upon various regions of the circumferences of the tag simultaneously, or must involve precise rotation of the wire as the marking operation takes place. Another drawback with Jefferts' marking system is that the pattern of circumferentially and axially spaced spots is only readable by a highly trained person, or requires the use of complex and expensive automated deciphering equipment. Another attempt at developing a coding system is disclosed in U.S. Pat. No. 4,233,964, to Jefferts et al., but this system also fails to overcome the drawbacks set forth above.
Yet another problem with prior systems is that in the process of injecting the wire tag into the fish, the tag typically passes through a needle-like device. While the interior surfaces of the needle are relatively smooth, they still may result in the identifying markings being marred or even partially obliterated. This problem has not yet been adequately addressed.
It is therefore an object of the invention to overcome the drawbacks and limitations of the prior art proposals. More specifically, the invention has as its objects:
(1) to provide a method for indelibly and clearly etching macro-organism tracing tags;
(2) to provide a system for marking tags which is suitable for highly automated, high speed marking;
(3) to develop a tagging system which does not require the use of wire tags;
(4) to provide a tagging system which includes a flattened face for easier marking and reading, and for reducing damage to the markings during injection into the macro-organisms; and
(5) to develop a tag marking system which can import a wide variety of characters to the tags; and
(6) to achieve the above objects while providing a system which is inexpensive, does not require a substantial amount of complex equipment, and does not involve a great deal of expertise on the part of the operator marking or reading the tag;